In Houston, a key dam on the Addicks Reservoir is overflowing. It's dumping extra water into the Buffalo Bayou west of the city and is likely to worsen flooding in the area. Shortly before 8 a.m. local time, the Addicks Reservoir began spilling over the top of the dam. Officials say it is the first time the Addicks' dam has ever overflowed like this. The Army Corps of Engineers began releasing water yesterday from the Addicks Reservoir and another reservoir after both reached record highs. Officials are also warning that a Columbia Lakes levy was breached by the flooding caused by Tropical Storm Harvey. Nearby residents are being warned that they should evacuate if possible.

RACHEL MARTIN, HOST:

Now the storm and the floods have spread to neighboring states as well. Tens of thousands of people have been forced from their homes, and the death toll is expected to rise. David, you've been in Houston since Sunday. Can you just give us a picture of what you've been seeing?

DAVID GREENE, HOST:

Yeah, we've sort of set up shop here at a hotel right along Interstate 45. And this three-story hotel, Rachel, it is just high enough that, you know, the lobby and first floor has not started to flood yet. But people have been watching closely. The parking lot, much of it is under water and the roads all around the hotel. And we're talking about much of it waist-deep water. So it's sort of a waiting game. But people who have made it to this hotel, safe at the moment.

MARTIN: So even if you wanted, needed to get out of that hotel in that area, could you?

GREENE: It's hard. I mean, some people have been coming in and out in these trucks with, like, these huge - the huge tires. We're talking, like, you know, monster trucks have been able to get in and deliver some food at times. But that's the hard thing for residents here. I mean, the ones who have gotten out were trying to make it from their flooded neighborhoods to a city like Dallas, but they got stuck.

And now they're here and wondering if they'll be able to get out from this hotel at some point. A lot of people have just been milling about, like, in the hotel lobby, coming outside, smoking cigarettes, getting to know each other, watching some dramatic moments. I mean, this guy who we spoke to, he described how he came out of this car that is now submerged in water on the road out in front. He's a relief worker. He was coming to help and got stuck in his car trying to make it to this hotel.

His car was filling with water. He pushed the door open and fortunately was able to wade through the water and get here.

BOB SENCERE: It seems like we're on an island here in the hotel now.

GREENE: It really does. So have you done a lot of relief work after floods and storms...

SENCERE: I have.

GREENE: ...And how does this compare?

SENCERE: Well, I've never been flooded before (laughter). I've been doing this for 15 years, and this is the first time that I've actually been caught in the flood itself so...

GREENE: That sort of tells you something. I mean, his name is Bob Sencere (ph). He's a disaster relief veteran and he, himself got his car stuck.

MARTIN: All right, I want to bring in another voice here. NPR's Nate Rott is in downtown Houston. Nate, so you made it downtown, which was a big deal. How was that journey? I mean, harrowing, I imagine.

NATHAN ROTT, BYLINE: Yeah, it was really touch and go. A lot of kind of flooded out roads, road closures that we kept running into. Here in downtown Houston, it's not anywhere near as dire as kind of what David's talking about. The flooding is not that bad. We saw far worse flooding along the entire route. We drove through a number of rural communities yesterday just trying to get into Houston, kind of jumping off of the freeway, taking some country roads, getting back on the freeway.

And we saw towns and people dealing with some of these issues a hundred miles to the west of the city, you know, flooding in low-lying areas, rivers that have just completely overrode their banks. We saw this field that had a bunch of cattle standing in knee-deep water, a golf course that was like a standing lake. I mean, you drive for a full day seeing those sort of impacts over such a huge area, and you really start to get an understanding of just the scale of this thing.

MARTIN: Yeah. And so many people have had to flee their homes for safety. Thousands are expected to be housed in these evacuation centers. I understand you got to go see one.

ROTT: Yeah, I got to see one of the biggest ones here in Houston. It's the George R. Brown Convention Center. It's right in the middle of downtown. It's been converted into an evacuation center for people who have been displaced with all of this. And it really was kind of a sad but also kind of a heartening scene last night. There were, you know, individuals and people coming in out of the pouring rain, getting dropped off by buses, family members or rescuers.

And one of the ladies that I talked to in the entrance of the center said she had waded through waist-deep water from her home with a bag of belongings on her back just to get picked up and brought there. When she got there, she was given dry clothes - most people were - and bedding that had been donated. And she was very grateful for that. It was kind of a happy scene for some people who had gotten there after being through such sort of harrowing experiences. I know that the Red Cross was expecting 3,000 evacuees at the evacuation center last night.

I don't know if there were that many people there. But there were certainly people still coming in when I left. And we should also say that's just one of many evacuation centers that have sprung up from here in Houston clear to Dallas and San Antonio.

MARTIN: Wow. So this thing isn't over yet either, right? The rain keeps coming - pictures, we're seeing, of rivers continuing to rise, people wading thigh-high trying to get across rivers and to safety or roads, rather, that have turned into rivers.

ROTT: Yeah, I mean, the big concern is that the storm kind of pinwheeled off the coast is coming back. And it's supposed to dump a lot more rain today. I just looked at the weather forecast, and it was saying that they're hoping that it'll start to let up maybe later this afternoon, this evening. But, I mean, some of these areas have seen more than 40 inches of rain. If it keeps raining today, we're going to be topping 50 inches.

CHANG: Wow.

ROTT: And I think there's things that are going to be a little slower developing, like rivers. You know, it'll take a couple of days for a river to fully crest. And when the waters recede, we'll start to see just how much damage there are in some of these places that have really been inundated.